From a8f347607a0f438afd5ac167930bbadb8aa17f74 Mon Sep 17 00:00:00 2001
From: Frank Hunleth <frank@smartrent.com>
Date: Sun, 13 Nov 2022 12:59:39 -0500
Subject: [PATCH] Fix references to mfa that should be mfargs

mfa = module, function, arity
mfargs = module, function, arguments

Dialyzer wasn't catching the use of `[any()]` in the tuple that was
typed to be `arity` (0..255) so this went unnoticed. This change just
clarifies that the user should pass arguments. I assume wasn't much of
an issue, since I think the A in MFA is frequently switched between
arguments and arity in libraries even though the `mfa()` type is pretty
clear that it's arity. MFArgs or `mfargs()` is how I've always seen the
argument version referred to when people make a distinction.
---
 README.md                 |  9 +++++----
 lib/ssh_subsystem_fwup.ex | 29 +++++++++++++++++------------
 2 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/README.md b/README.md
index 1056d42..78697aa 100644
--- a/README.md
+++ b/README.md
@@ -128,10 +128,11 @@ The following options are available:
 * `:fwup_env` - a list of name,value tuples to be passed to the OS environment for fwup
 * `:fwup_extra_options` - additional options to pass to fwup like for setting
   public keys
-* `:precheck_callback` - an MFA to call when there's a connection. If specified,
-  the callback will be passed the username and the current set of options. If allowed,
-  it should return `{:ok, new_options}`. Any other return value closes the connection.
-* `:success_callback` - an MFA to call when a firmware update completes
+* `:precheck_callback` - an MFArgs to call when there's a connection. If
+  specified, the callback will be passed the username and the current set of
+  options. If allowed, it should return `{:ok, new_options}`. Any other return
+  value closes the connection.
+* `:success_callback` - an MFArgs to call when a firmware update completes
   successfully. Defaults to `{Nerves.Runtime, :reboot, []}`.
 * `:task` - the task to run in the firmware update. Defaults to `"upgrade"`
 
diff --git a/lib/ssh_subsystem_fwup.ex b/lib/ssh_subsystem_fwup.ex
index 0c66191..1d6c369 100644
--- a/lib/ssh_subsystem_fwup.ex
+++ b/lib/ssh_subsystem_fwup.ex
@@ -32,6 +32,11 @@ defmodule SSHSubsystemFwup do
   device-specific.
   """
 
+  @behaviour :ssh_client_channel
+
+  @typedoc false
+  @type mfargs() :: {module(), function(), [any()]}
+
   @typedoc """
   Options:
 
@@ -40,22 +45,22 @@ defmodule SSHSubsystemFwup do
   * `:fwup_env` - a list of name,value tuples to be passed to the OS environment for fwup
   * `:fwup_extra_options` - additional options to pass to fwup like for setting
     public keys
-  * `:precheck_callback` - an MFA to call when there's a connection. If specified,
-    the callback will be passed the username and the current set of options. If allowed,
-    it should return `{:ok, new_options}`. Any other return value closes the connection.
-  * `:success_callback` - an MFA to call when a firmware update completes
+  * `:precheck_callback` - an MFArgs to call when there's a connection. If
+    specified, the callback will be passed the username and the current set of
+    options. If allowed, it should return `{:ok, new_options}`. Any other
+    return value closes the connection.
+  * `:success_callback` - an MFArgs to call when a firmware update completes
     successfully. Defaults to `{Nerves.Runtime, :reboot, []}`.
   * `:task` - the task to run in the firmware update. Defaults to `"upgrade"`
   """
-  @behaviour :ssh_client_channel
   @type options :: [
           devpath: Path.t(),
           fwup_path: Path.t(),
           fwup_env: [{String.t(), String.t()}],
           fwup_extra_options: [String.t()],
-          precheck_callback: mfa() | nil,
+          precheck_callback: mfargs() | nil,
           task: String.t(),
-          success_callback: mfa()
+          success_callback: mfargs()
         ]
 
   require Logger
@@ -182,15 +187,15 @@ defmodule SSHSubsystemFwup do
     {:noreply, state}
   end
 
-  defp run_callback(0 = _rc, {m, f, a}) do
+  defp run_callback(0 = _rc, {m, f, args}) do
     # Let others know that fwup was successful. The usual operation
     # here is to reboot. Run the callback in its own process so that
     # any issues with it don't affect processing here.
-    _ = spawn(m, f, a)
+    _ = spawn(m, f, args)
     :ok
   end
 
-  defp run_callback(_rc, _mfa), do: :ok
+  defp run_callback(_rc, _mfargs), do: :ok
 
   @impl :ssh_client_channel
   def terminate(_reason, _state) do
@@ -212,8 +217,8 @@ defmodule SSHSubsystemFwup do
 
   defp precheck(nil, options), do: {:ok, options}
 
-  defp precheck({m, f, a}, options) do
-    case apply(m, f, a) do
+  defp precheck({m, f, args}, options) do
+    case apply(m, f, args) do
       {:ok, new_options} -> {:ok, Keyword.merge(options, new_options)}
       {:error, reason} -> {:error, reason}
       e -> {:error, "precheck failed for unknown reason - #{inspect(e)}"}